Various kinds of combustible materials are contained in a secondary battery. As a result, the secondary battery may be heated or explode due to overcharge of the secondary battery, overcurrent in the secondary battery, or other physical external impact applied to the secondary battery. That is, the safety of the secondary battery is very low. Consequently, safety elements, such as a positive temperature coefficient (PTC) element and a protection circuit module (PCM), to effectively control an abnormal state of the secondary battery, such as overcharge of the secondary battery or overcurrent in the secondary battery, are disposed on a battery cell in a state in which the safety elements are connected to the battery cell.
Meanwhile, a conventional battery pack for laptop computers is manufactured by electrically connecting several secondary batteries exhibiting high flexibility in series or in parallel to each other and connecting the secondary batteries to a protection circuit by welding to manufacture a battery cell assembly, which is called a soft pack, and enclosing the battery cell assembly in a plastic pack case so as to protect the battery cell assembly from external impact or provide an aesthetically pleasing appearance.
In the method of manufacturing the conventional battery pack for laptop computers as described above, however, it is difficult to assemble the battery pack due to high flexibility of the secondary batteries.
Also, a bonding agent or a double-sided adhesive tape is provided between the pack case and the secondary batteries so as to prevent the secondary batteries from moving in the pack case after the battery pack is assembled. As a result, the number of parts constituting the battery pack is increased, and the battery pack manufacturing process is complicated. In addition, the secondary batteries move in the pack case when external impact is applied to the battery pack with the result that the battery pack may malfunction.
Therefore, there is a high necessity for a battery cell assembly having a specific structure that is capable of solving assembly complexity, which is caused when the battery pack for laptop computers with the above-stated construction is manufactured, and preventing movement of battery cells, such as secondary batteries, in a pack case, which is also caused when the battery pack for laptop computers with the above-stated construction is manufactured.
Meanwhile, a battery pack mounted in a laptop computer requires high power and capacity. To this end, a conventional cylindrical battery pack including a plurality of cylindrical battery cells has generally been used. In recent years, however, the size of a laptop computer has been reduced, and therefore, there is a high necessity for a slim type battery pack.
Therefore, there is a high necessity for a technology that is capable of using high capacity pouch-shaped battery cells to manufacture a slim type battery pack, thereby increasing overall current capacity of the battery pack.